46 C.F.R. § 108.699
Substitution of life preservers
A work vest may not be substituted for a required life preserver—
(a) For the life saving equipment requirements of this part; or
(b) For use during drills and emergencies.
A work vest may not be substituted for a required life preserver—
(a) For the life saving equipment requirements of this part; or
(b) For use during drills and emergencies.